The present disclosure relates to wellbore signal monitoring devices and techniques. More specifically, the present disclosure relates to the positioning of seismic sensors on or near drill tools for optimizing monitored signals by reducing unwanted tube-wave noise.
In the measurement of seismic signals originating from outside of a wellbore, multi-component seismic sensors may be positioned within the wellbore for microseismic monitoring, seismic surveying, and permanent monitoring. A sampling of seismic techniques is provided in WO2007105167, entitled “Method and Apparatus for Hydraulic Fracturing and Monitoring,” U.S. Pat. No. 5,503,225, entitled “System and Method for Monitoring the Location of Fractures in Earth Formations,” WO1989007774, entitled “Method for Vertical-Seismic Profiling in Wells,” U.S. Pat. No. 7,813,220, entitled “Method and Apparatus for Long Term Seismic Monitoring,” and U.S. Pat. No. 6,981,550, entitled “Sonde.”
Tube waves may be present during seismic operations, and may affect wellbore signal surveys. When the tube wave is present in the wellbore, the signal-to-noise (S/N) ratio of the signal of interest as received by seismic sensors within the wellbore may be deteriorated.
Seismic sensors used for signal monitoring within a wellbore may be housed in one package elongated to an axial direction for insertion and use within the wellbore. Techniques related to sensor packaging are provided in WO2001099028, entitled “Orthogonal Triaxial Acoustic Receiver,” WO2002068996, entitled “Seismic Detection Using 4-Sensors,” and U.S. Pat. No. 6,981,550, entitled “Sonde.” With regard to such axial orientations, the direction of motion of the tube wave may have strong radial components that may propagate axially within the wellbore. In other words, unwanted tube wave energy may be excited in the radial direction. The tube-wave energy may also be excited to a lesser extent in the tangential and axial directions. Attempts may be made to reduce the tube-tube wave noise and to enhance signal quality in connection with wellbore signal monitoring processes. Techniques pertaining to tube-wave noise reduction in a borehole are provided in WO2000075694, entitled “Acoustic Isolator for Downhole Applications,” WO2007118210, entitled “Improved Performance of Permanently Installed Tubing Conveyed Seismic Arrays Using Passive Acoustic Absorbers,” US20040238266, entitled “Methods and Apparatus of Suppressing Tube Waves within a Bore Hole and Seismic Surveying Systems Incorporating Same,” and U.S. Pat. No. 6,181,642, entitled “Apparatus and Method for Borehole Seismic Exploration.” Packing the seismic sensors into one package elongated to the axial direction may result in retaining of the radial component of the tube-noise wave field for three-component monitoring.